The application of the SSES SEM-based analytic approach to neuroscience primarily involves collaborating with neuroscientists in developing and carrying out analyses testing their hypotheses and elucidating their data when more traditional forms of analysis are inadequate. One such longstanding collaboration is with the NINDS Cognitive Neuroscience Section (CNS). The collaboration?s centers on the analysis of longitudinal data from the Vietnam Head Injury Study (VHIS)-- an intensive long term study of the effects of penetrating head injury that includes matched normal controls. Our collaboration?s present focus is on a survey, based on the SSES longitudinal survey, that the CNS is carrying out as part of the present wave of VHIS data collection. Analyzed in conjunction with other VHIS data these survey data will permit the examination of the interactions among environmental demands, brain injury location and APOE and COMT alleles in affecting psychological functioning. A second collaboration is with the NIMH Laboratory of Clinical Science. Through SEM and related analyses we reliably ascertained the latent factorial structure of Obsessive Compulsive Disorder (OCD), used the factors? pattern of interrelationships to distinguish different OCD subgroups and linked group membership to differences in familial incidence and comorbidity.